A festoon style lamp is one that is suspended between two points. Typically, festoon lamps have electrical contacts members (e.g., “bases” or “end caps” formed of conductive material such as aluminum or nickel-plated brass) on either end of an elongate cylindrical glass tube. In traditional incandescent festoon lamps, the glass tube is filled with a suitable gas and a filament, typically a tungsten filament, is positioned within the glass tube coincident with its longitudinal axis. The feston lamp is held in place by inseting its electrical contact members into spaced apart contacts that are configured to receive and to energize the lamp.
U.S. Pat. No. 5,207,503 (McLaughlin) describes festoon lamps of the foregoing general character that contain xenon gas. The xenon lamp has cylindrical, conical tipped end caps, a tungsten filament, and a cylindrical bulb. The end caps are made of conductive material such as aluminum or nickel-plated brass, and are designed to adapt the lamp to fit into spade shaped contacts.
United States Patent Application Publication No. 20070076428 (Wu) describes a festoon lamp which comprises a light-permeable tube with two electrode contacts respectively installed at two ends of the light-permeable tube. A light-conducting element is installed inside the light-permeable tube and two light sources are respectively installed at two ends of the light-conducting element and respectively coupled to the two electrode contacts. This lamp is purported to use minimum light sources to obtain a large light-emitting area, thereby reducing power consumption.
In recent years, the use of LED's in various lighting applications has grown. LED's are solid state lamps that use semiconductor material instead of a filament or neon gas. When compared to traditional (i.e., fluorescent or incandescent) light bulbs, LED's offer a number of advantages. For example, because LED's operate on low voltage and consume less power, they are less expensive to operate and generate significantly less heat than traditional light bulbs. Also, because LED's are of solid state design, they are more durable and less likely to break than traditional bulbs. Another advantage of LED's is their long life. Some LED lamps can operate for up to 100,000 hours, compared to about 1500 hours for a standard filament light bulb. Moreover, LED's are environmentally friendly, contain no mercury and produce no electromagnetic emissions. Another advantage is that a single LED bulb can produce many different colors without the need for colored coatings or lenses. In view of their numerous advantages, LED's are being used in many applications where fluorescent or incandescent lighting was previously used. However, because LED's generate substantial amounts of heat, their applications in tradition festoon type lamps has been limited to relatively low output LED's (e.g., less than ½ watt). Others have proposed heat dissipation apparatus for dissipating the heat from LED's in festoon lamps. For example, United States Patent Application Publication No. 20050258440 (Dry) describes light emitting diode (LED) light sources including festoon lamps wherein an LED is carried on a surface of a heat transfer member or heat sink fabricated from aluminum or other material having efficient heat transfer properties. The heat sink is configured to transfer heat from the LED to fluid that is contained by or surrounds the thermally conductive member(s). However, in this system, the heat sink itself is electrically conductive and the end caps or bases of the feston lamp are mounted on the ends of the heat sink. Also, in the examples shown in United States Patent Application Publication No. 20050258440 (Dry), components of the festoon lamp extend upwardly from the circuit board, above the upper edges of the ends caps, thus potentially limiting the ability of the feston lamp to rotate within a confined or enclosed fixture or space.
There remains a need in the art for the development of new festoon type LED lamps having improved heat dissipation capabilities sufficient to enable the use of “power” LEDS of greater than ½ watt and which, in at least some applications, may be powered by alternating current (AC) and which may be configured to have a low profile to allow free rotation of the festoon lamp within a confined or enclosed fixture or space.